1. Field of the Invention
The invention relates to a mobile phone terminal to which an intelligent battery pack can be attached as power supply, and a communication system including the mobile phone terminal and the intelligent battery pack incorporated therein. Specifically, the invention relates to communication technology for a mobile phone terminal communicating with the battery incorporated therein.
2. Description of the Related Art
In battery packs incorporated in mobile phone terminals as a power supply, there is provided an intelligent battery pack capable of determining status of a rechargeable battery contained therein based on the self-gauged voltage, current, temperature and the like, and transferring such data to the mobile phone terminal via communication terminals. The intelligent battery pack sends self-gauged data, such as remaining battery capacity, to the mobile phone terminal at each of predetermined time intervals.
A serial interface is utilized for transmitting and receiving data between the intelligent battery pack and mobile phone terminal. Japanese Unexamined Patent Application Publication No. 2007-0058347 discloses a serial communications apparatus called Universal Asynchronous Receiver Transmitter (UART) known as an asynchronous serial communications circuit.
Asynchronous serial communication involves a communication system for synchronizing data communication between the intelligent battery pack and the mobile phone terminal. In this system, when there is no information, such as characters, to be sent, a stop bit is consecutively transmitted (normally, direct current voltage), whereas when there is, one bit is sent prior to each information that is subject to transmission. In this system, synchronous operation is not always required for data communication; that is, synchronous operation is only carried out upon request.
Japanese Unexamined Patent Application Publication No. 2007-0058347 discloses communication technology for reducing power consumption for a serial communication apparatus. The disclosed technology includes: consecutively supplying external clock signals; maintaining a standby status for receiving data while receiving no data; and generating a clock controller activating signal triggered by data reception so as to reduce power consumption for a serial communication apparatus.